• Title/Summary/Keyword: 한국수화

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Control of Phythophthora capsici and Residual Characteristics by the Pesticides Tank-Mixed in Tomato Hydroponic Culture System (농약의 양액 탱크내 혼합처리에 의한 토마토 역병 방제 효과 및 잔류 특성)

  • Ihm, Yang-Bin;Kyung, Kee-Sung;Kim, Cban-Sub;Park, Byung-Jun;Lee, Jung-Sup
    • The Korean Journal of Pesticide Science
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    • v.7 no.4
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    • pp.264-270
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    • 2003

  • To control effectively and safely Phytophthora root rot caused by Phytophthora capsici on tomato in hydroponic culture, tank-mixing method was considered with two pesticides, metalaxyl copper oxychloride 50% WP and dimethomorph dithianon 38% WP. Forty days after transplanting of tomato seedlings, 4 mL of sporangia of P. capsici (about 25 sporangi/mL) per plot was inoculated around tomato plant roots, and at 5 days after inoculation, the pesticides tank-mixed at three dilution levels, 12,500, 25,000 and 50,000, were drenched 1, 2 or 3 times per plot on the culture cube every 15 days for metalaxyl copper oxychloride 50% WP and every 10 days for dimethomorph dithianon 38% WP. During the drenching period, the residue levels of metalaxyl and dimethomorph in hydroponic culture solution were similar to the initial levels but the level of dithianon was drastically decreased from one day after tank-mixing. In tomato drenched with metalaxyl copper oxychloride 50% WP, metalaxyl was detected $0.02\sim0.04$ mg/kg in all diluted plots. Dimethomorph was detected $0.012\sim0.021$, $0.001\sim0.006$ and $0.001\sim0.003$ mg/kg in 12,500, 25,000 and 50,000 times diluted plots, respectively, while dithianon was detected 0.005, 0.003 mg/kg in 12,500 and 50,000 times diluted plots, respectively. The detection levels of three pesticides were far below compared with the levels of Korean MRLs. Incidences of Phytophthora root rot were not found in all the plots, but phytotoxic responses were recognized in the 12,500 times diluted plots of both pesticides. Based on the above results, the drenching of the culture solution tank-mixed with these pesticides could be recommended as a very safe and effective method to control Phytophthora root rot in tomato in hydroponic culture.

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Effect of Hardening Accelerators on the Adiabatic Temperature property Properties of Precast Concrete and FEM analysis for Evaluating the Crack Performance (경화촉진제를 사용한 프리캐스트 콘크리트의 단열온도특성 및 FEM해석에 의한 균열성능 평가에 관한 연구)

  • Min, Tae-Beom;Cho, In-Sung;Mun, Young-Bum;Lee, Han-Seung
    • Journal of the Korea Institute of Building Construction
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    • v.15 no.1
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    • pp.25-33
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    • 2015

  • In this study, initial crack index was evaluated by FEM analysis to find the crack propagation from hydration heat in precast concrete. As results, as the usage of hardening accelerator increased, initial compressive strength increased and setting time was shortened. Additionally, as amounts of hardening accelerators increased, the central temperature of concrete increased and the time to reach the highest temperature was shortened. It was demonstrated that the hardening accelerators accelerated the hydration reaction of cement, and caused the increase of hydration heat within the short period of time. Furthermore, the crack index for evaluating the heat level was performed by FEM. As results, there was no problem about the cracks, despite of the growth of initial high hydration heat. This is because of the increased tensile strength that is large enough to sustain the thermally induced-stress.

  • https://doi.org/10.5345/JKIBC.2015.15.1.025 인용 PDF KSCI

Changes in Hydration and Watertightness of Cement Containing Two-Component Fluosilicate Salt Based Chemical Admixture (2성분 규불화염계 혼화제가 첨가된 시멘트의 수화반응 및 수밀성 변화)

  • Kim, Jae-On;Nam, Jae-Hyun;Kim, Do-Su;Khil, Bae-Su;Lee, Byoung-Ky
    • Journal of the Korean Ceramic Society
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    • v.41 no.10 s.269
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    • pp.749-755
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    • 2004

  • Fluosilicic acid ($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicate salts prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicate salts to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. In this study, two-component fluosilicate salt based chemical admixtures (MZ) of $4\%,\;6\%$, and $8\%$ concentration were prepared by the reaction of $H_2SiF_6$ ($25\pm2\%$) and metal salts. The effect of concentration of MZ at a constant adding ratio on the hydration and watertightness of cement were investigated respectively. In a cement containing MZ, metal fluorides such as $CaF_2$ and soluble silica by hydrolysis were newly formed during hydration. The total porosity of the hardened cement was lower in the presence of U because of packing role of metal fluoride and pozzolanic reaction of soluble $SiO_2$. Consequently, the watertightness of the hardened paste containing MZ was more improved than non-added (plain) due to an odd hydration between cement and MZ.

  • https://doi.org/10.4191/KCERS.2004.41.10.749 인용 PDF KSCI